1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device and, more particularly, to a method of manufacturing a semiconductor device which prevents a metal layer having a high point of fusion from incompletely filling a contact hole.
2. Description of Related Art
Generally, with the high integration of semiconductor devices, the size of a source/drain and a line width of a gate electrode of a MOS transistor and a line width of metal layer are reduced. In particular, when the line width of the metal layer is reduced, a size of a contact hole is also reduced. The contact hole is either for contacting the gate electrode and the metal layer or for contacting the source/drain and the metal layer. Since contact resistances of the gate electrode and the metal layer are increased, the resistance of the metal layer is also increased. Consequently, the operation speed of the semiconductor device is reduced. However, there is great demand for a semiconductor device with enhanced speed together with high integration.
In one scheme for satisfying this demand, a metal layer of a high fusion, e.g. tungsten (W) layer has been used to reduce the contact resistance. To reduce contact resistance of the tungsten layer and the contact region, a barrier metal is formed between the tungsten layer and the contact region.
In the conventional semiconductor device, shown in FIG. 1, an insulating layer 11 is deposited on a semiconductor substrate 10, a contact hole 12 is formed on a contact region of the semiconductor substrate 10, a barrier metal 13 is deposited on the insulating layer 11 and in the contact hole 12, and a tungsten layer 15 is deposited on the barrier metal 13 to fill the contact hole 12.
In the prior art, a TiN or WN layer, is used as a barrier metal 13 and is deposited on the insulating layer 11 and in the contact hole 12 by a sputtering process. However, as the size of the contact hole 12 is reduced below 0.2 μm and the aspect ratio thereof is increased above 5, it is more difficult to continuously perform deposition of the barrier metal 13 on the entire surface in the contact hole 12. Accordingly, the barrier metal 13 is hardly deposited on the bottom face of the contact hole 12. In this state, since the tungsten layer 15 cannot completely fill the contact hole, a void 16 forms in the lower portion of the contact hole 12. Thus, a contact defect occurs in the contact hole 12, which can produce numerous defects. An electrical disconnect may be generated in the contact hole 12. The reliability of the metal layer due to an electro migration or a stress migration may also be reduced.
In order to solve this problem, various methods using WSiN layer as a barrier metal have been proposed, but the methods still have many problems.